{"paper":{"title":"PKS 2131-021 -- Discovery of Strong Coherent Sinusoidal Variations from Radio to Optical Frequencies: Compelling Evidence for a Blazar Supermassive Black Hole Binary","license":"http://creativecommons.org/licenses/by/4.0/","headline":"","cross_cats":[],"primary_cat":"astro-ph.HE","authors_text":"A. C. S. Readhead, A. G. Sullivan, A. Synani, B. Molina, C. P. O'Dea, C. R. Lawrence, D. C. Homan, F. Harrison, I. Liodakis, J. A. Zensus, K. Chatziioannou, K. Tassis, M. C. Begelman, M. F. Aller, M. J. Graham, M. L. Lister, M. Vallisneri, P. Mr\\'oz, P. V. de la Parra, R. A. Reeves, R. D. Blandford, R. Maiolino, S. Kiehlmann, S. K. N{\\ae}ss, S. O'Neill, S. R. Kulkarni, T. A. Prince, T. Hovatta, T. J. Pearson, T. J. W. Lazio, V. Pavlidou, V. Ravi, W. Max-Moerbeck, Y. Ding","submitted_at":"2024-07-12T19:05:24Z","abstract_excerpt":"Haystack and Owens Valley Radio Observatory (OVRO) observations recently revealed strong, intermittent, sinusoidal total flux-density variations that maintained coherence between 1975 and 2021 in the blazar PKS 2131$-$021 ($z=1.283$). This was interpreted as possible evidence of a supermassive black hole binary (SMBHB). Extended observations through 2023 show coherence over 47.9 years, with an observed period $P_\\textrm{15 GHz}=(1739.8 \\pm 17.4)$ days}. We reject, with $p$-value = $2.09 \\times 10^{-7}$, the hypothesis that the variations are due to random fluctuations in the red noise tail of "},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"2407.09647","kind":"arxiv","version":2},"verdict":{"id":null,"model_set":{},"created_at":null,"strongest_claim":"","one_line_summary":"","pipeline_version":null,"weakest_assumption":"","pith_extraction_headline":""},"integrity":{"clean":true,"summary":{"advisory":0,"critical":0,"by_detector":{},"informational":0},"endpoint":"/pith/2407.09647/integrity.json","findings":[],"available":true,"detectors_run":[],"snapshot_sha256":"c28c3603d3b5d939e8dc4c7e95fa8dfce3d595e45f758748cecf8e644a296938"},"references":{"count":0,"sample":[],"resolved_work":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57","internal_anchors":0},"formal_canon":{"evidence_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"author_claims":{"count":0,"strong_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"builder_version":"pith-number-builder-2026-05-17-v1"}